Humidifier for breathing gas heating and humidification system

ABSTRACT

A humidification canister for humidifying a breathing gas, the humidification canister includes a fluid supply configured to supply a fluid and a first gas flow path in fluid communication with the fluid supply. A first gas flow path is configured to humidify the breathing gas with the fluid. A second gas flow path at least partially surrounds the first gas flow path. A method of insulating a breathing gas in a humidification canister using a gas is also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/929,879, filed on Jul. 15, 2020, which is a continuation of U.S.patent application Ser. No. 14/184,202, filed on Feb. 19, 2014 (now U.S.Pat. No. 10,786,646), which is a continuation of U.S. patent applicationSer. No. 12/175,888, filed on Jul. 18, 2008 (now U.S. Pat. No.8,677,993), which claims the priority to and benefit of U.S. ProvisionalPatent Application No. 60/981,270 (now expired), filed on Oct. 19, 2007,and U.S. Provisional Patent Application No. 60/961,020 (now expired),filed on Jul. 18, 2007. This application is related to U.S. patentapplication Ser. No. 12/175,861, filed on Jul. 18, 2008 (now U.S. Pat.No. 8,333,195); U.S. patent application Ser. No. 12/175,853, filed onJul. 18, 2008 (now U.S. Pat. No. 8,240,306) and U.S. patent applicationSer. No. 12/175,899, filed on Jul. 18, 2008 (now U.S. Pat. No.8,356,593). The entire contents of the above-referenced applications areincorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to respiratory tract therapy. More particularly,this invention relates to methods and apparatus that heat and humidify abreathing gas for delivery to the respiratory tract of a patient.

BACKGROUND OF THE INVENTION

Conventional methods of delivering gas (e.g., air, oxygen,oxygen-enriched air, and other breathing gas mixtures) to therespiratory tract of a patient often result in discomfort to thepatient, especially when the gases are delivered over an extended periodof time. A need remains for improved methods and apparatus fordelivering breathing gas.

BRIEF SUMMARY OF THE INVENTION

Briefly, the present invention provides an apparatus for providingbreathing gas to a patient. The apparatus includes a base unitconfigured to provide a first flow of gas and a second flow of gas and ahumidification canister configured to be coupled to the base unit. Thehumidification canister includes a first gas flow path configured toreceive and humidify the first flow of gas. A delivery tube assembly isconfigured to be coupled to the humidification canister. The deliverytube assembly includes a first lumen configured for fluid communicationwith the first gas flow path to receive the humidified first flow of gasand a second lumen configured to receive the second flow of gas.

The present invention also provides a heated and humidified breathinggas apparatus including a source of gas and a humidification chamberoperatively coupled to the source of gas. The humidification chamber isconfigured to heat and humidify a first portion of the gas generated bythe source of gas. An insulation chamber is operatively coupled to thesource of gas and at least partially surrounds the humidificationchamber. A multilumen delivery tube assembly has a first lumen in fluidcommunication with the humidification chamber and a second lumenadjacent the first lumen in fluid communication with the insulationchamber.

Further, the present invention provides a method for providing breathinggas to a patient that includes generating a first flow of gas and asecond flow of gas; passing the first flow of gas along a first gas flowpath and the second flow of gas along a second gas flow path,humidifying the first flow of gas in the first gas flow path, insulatingat least a portion of the first flow of gas passing along the first gasflow path with the second flow of gas passing along the second gas flowpath, and delivering the humidified first flow of gas to the patient forinhalation by the patient.

Additionally, the present invention provides a method of deliveringheated and humidified breathing gas to a patient. The method includesgenerating a gas flow, dividing the gas flow into a breathing gas flowand an insulating gas flow, heating and humidifying the breathing gasflow, and delivering the heated and humidified breathing gas flow to thepatient.

Further, the present invention provides a base unit for use in abreathing gas heating and humidification apparatus. The base unitincludes a gas source configured to generate an initial gas flow. Thegas source has a gas source outlet. A flow divider is in fluidcommunication with the gas source outlet. The flow divider is configuredto divide the initial gas flow into a first flow of gas and a secondflow of gas. The flow divider includes a first compartment including afirst gas flow path for the first flow of gas and a second compartmentincluding a second gas flow path for the second flow of gas. A heater isdisposed in the second compartment.

Also, the present invention provides a base unit for use in a breathinggas heating and humidification apparatus. The base unit includes ablower configured to generate a gas flow and a flow divider in fluidcommunication with the blower. The divider is configured to divide thegas flow into a first portion of the gas flow and a second portion ofthe gas flow.

The present invention further provides a method for use in generatingbreathing gas and insulating gas from a gas source. The method includesgenerating a flow of gas, dividing the flow of gas into a first flow ofgas and a second flow of gas, and passing the first flow of gas fordelivery to a patient for inhalation.

Additionally, the present invention provides a humidification canisterfor humidifying a breathing gas. The humidification canister includes afluid supply configured to supply a fluid. A first gas flow path is influid communication with the fluid supply. The first gas flow path isconfigured to humidify the breathing gas with the fluid. A second gasflow path at least partially surrounds the first gas flow path.

The present invention further provides a method of pressurizing a supplyof humidification fluid within a humidification that includes generatinga flow of a breathing gas along a first gas flow path, generating a flowof an insulating gas along a second gas flow path, providing a supply ofa humidification fluid within the humidification canister to humidifythe breathing gas, and providing fluid communication between the secondgas flow path and the supply of the humidification fluid to pressurizethe supply of the humidification fluid with the insulating gas.

The present invention also provides a method of insulating a breathinggas in a humidification canister using a gas. The method includesdirecting a flow of a breathing gas along a first gas flow pathincluding the humidification chamber and directing a flow of aninsulating gas along a second gas flow path including an insulatingchamber at least partially surrounding the humidification chamber wherethe insulating gas at least partially insulates the breathing gas.

Additionally, the present invention provides a humidification canisterfor humidifying a flow of breathing gas. The humidification canisterincludes means for supplying a fluid, means for humidifying a first gasflow with the fluid along a first gas flow path, and means for at leastpartially insulating the first gas flow with a second gas flow.

Further, the present invention provides a delivery tube assembly fordelivering a breathing gas to a patient. The delivery tube includes afirst lumen having an upstream portion and a downstream portion. Thelumen is configured to deliver the breathing gas from the upstreamportion to the downstream portion. A second lumen is configured to flowan insulating gas around the first lumen.

The present invention also provides a delivery tube assembly configuredto be coupled to a humidifier. The delivery tube assembly comprises aninner lumen with an upstream portion configured to receive humidifiedbreathing gas from the humidifier and a downstream portion configured todeliver the humidified breathing gas to a breathing device and an outerlumen surrounding the inner lumen that is configured for coupling to thehumidifier to receive an insulating gas.

The present invention further provides a delivery tube assembly fordelivering a breathing gas to a patient. The delivery tube includes aninner lumen adapted to transmit a breathing gas and an outer lumen atleast partially surrounding the inner lumen. The outer lumen is adaptedto transmit an insulating gas and discharge the insulating gas toatmosphere. A diverter assembly is positioned to divert the insulatinggas being discharged from the outer lumen to the atmosphere.

Further, the present invention provides a method of insulating heatedand humidified breathing gas with an insulating gas in a delivery tubeassembly having a first lumen and a second lumen. The method includesflowing the heated and humidified breathing gas through the first lumenand flowing the insulating gas through the second lumen where theinsulating gas at least partially insulates the heated and humidifiedbreathing gas.

Also, the present invention provides a method of insulating a breathinggas with an insulating gas and discharging the insulating gas toatmosphere. The method includes receiving the breathing gas in anupstream end of a delivery tube; receiving the insulating gas in theupstream end of the delivery tube; discharging the breathing gas from adownstream end of the delivery tube into a breathing device; flowing theinsulating gas from the upstream end of the delivery tube, through thedelivery tube, to the distal end of the delivery tube; and dischargingthe insulating gas from the delivery tube to atmosphere.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofexemplary embodiments of the invention, will be better understood whenread in conjunction with the appended drawings, which are incorporatedherein and constitute part of this specification. For the purposes ofillustrating the invention, there are shown in the drawings exemplaryembodiments of the present invention. It should be understood, however,that the invention is not limited to the precise arrangements andinstrumentalities shown. In the drawings, the same reference numeralsare employed for designating the same elements throughout the severalfigures. In the drawings:

FIG. 1 is a perspective view of an apparatus for providing breathing gasto a user according to a first exemplary embodiment of the presentinvention;

FIG. 2 is a side view, partially in section, of the breathing gasapparatus of FIG. 1;

FIG. 3 is a side view of a blower and gas heater illustrated in FIG. 2;

FIG. 3A is a schematic view of a first gas flow path and a second gasflow path through the breathing gas apparatus illustrated in FIG. 1;

FIG. 4 is a top view of a bottom portion of the base unit of theapparatus illustrated in FIG. 1;

FIG. 5 is a side exploded view of elements of the base unit of theapparatus illustrated in FIG. 1;

FIG. 6 is an exploded perspective view of a gas heater used in theapparatus illustrated in FIG. 1;

FIG. 7 is a perspective view of the gas heater illustrated in FIG. 6,with a box portion of the gas heater removed;

FIG. 8 is a perspective view of the gas heater illustrated in FIG. 7,with an insulator board portion of the gas heater removed;

FIG. 9 is a schematic drawing of an exemplary control system used tooperate the apparatus illustrated in FIG. 1;

FIG. 10 is a perspective view of a humidification canister used in theapparatus illustrated in FIG. 1;

FIG. 11 is an exploded side view of the humidification canisterillustrated in FIG. 10;

FIG. 12 is a perspective view of a filter media used in thehumidification canister illustrated in FIGS. 10 and 11;

FIG. 12A is a top plan view of the filter media illustrated in FIG. 12;

FIG. 13 is a perspective view of a media holder used in thehumidification canister illustrated in FIGS. 10 and 11;

FIG. 13A is a top plan view of the media holder illustrated in FIG. 13;

FIG. 14 is a perspective view of a fluid supply reservoir used in thehumidification canister illustrated in FIGS. 10 and 11;

FIG. 14A is a top plan view of the fluid supply reservoir illustrated inFIG. 14;

FIG. 15 is a perspective view of a lid bottom used in the humidificationcanister illustrated in FIGS. 10 and 11;

FIG. 15A is a top plan view of the lid bottom illustrated in FIG. 15;

FIG. 16 is a schematic view of an apparatus for providing breathing gasto a user according to an alternative exemplary embodiment of thepresent invention;

FIG. 17 is a side view, partially broken away, of a delivery tubeassembly used in the apparatus illustrated in FIG. 1;

FIG. 18 is an exploded side view of the delivery tube assemblyillustrated in FIG. 17;

FIG. 19 is a perspective view of an exemplary spacer used in thedelivery tube assembly illustrated in FIGS. 17 and 18;

FIG. 20 is a top plan view of the spacer illustrated in FIG. 19;

FIG. 21 is a perspective view of a twist lock connection used in thedelivery tube assembly illustrated in FIGS. 17 and 18;

FIG. 22 is a side view of the twist lock connection illustrated in FIG.21;

FIG. 23 is an end view of the twist lock connection illustrated in FIG.21;

FIG. 24 is a perspective view of a downstream end of the delivery tubeassembly illustrated in FIGS. 17 and 18;

FIG. 25 is an exploded perspective view of a diverter assembly used inthe delivery tube assembly illustrated in FIGS. 17 and 18;

FIG. 26 is a side view, in section, of the diverter assembly illustratedin FIG. 24;

FIG. 27 is a flow chart illustrating exemplary operational steps of theapparatus illustrated in FIGS. 1-26;

FIG. 28 is a schematic drawing of an apparatus for providing breathinggas to a user according to another exemplary embodiment of the presentinvention;

FIG. 29 is a schematic drawing of an apparatus for providing breathinggas to a user according to another exemplary embodiment of the presentinvention;

FIG. 30 is a sectional view of a delivery tube assembly according toanother exemplary embodiment of the present invention;

FIG. 31 is a sectional view of a delivery tube assembly according to yetanother exemplary embodiment of the present invention;

FIG. 32 is a schematic view of an apparatus for providing breathing gasto a user using the delivery tube assembly illustrated in FIG. 31according to another exemplary embodiment of the present invention; and

FIG. 33 is a schematic view of an apparatus for providing breathing gasto a user according to another exemplary embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

Although the invention is illustrated and described herein withreference to specific embodiments, the invention is not intended to belimited to the details shown. Rather, various modifications may be madein the details within the scope and range of equivalents of thedisclosure without departing from the invention. As used herein, theterm “upstream” is defined to mean a direction farther from a user(i.e., a person receiving breathing gas) along a fluid flow path, andthe term “downstream” is defined to mean a direction closer to the useralong the fluid flow path. The terms “insulate,” “insulating,” and“insulation” are used herein to mean preventing or reducing temperatureloss in fluid flowing along a fluid flow path, and/or, in certaincircumstances, raising the temperature of the fluid flowing along thefluid flow path.

The invention is best understood from the following detailed descriptionwhen read in connection with the accompanying drawing figures, whichshow exemplary embodiments of the invention selected for illustrativepurposes. The invention will be illustrated with reference to thefigures. Such figures are intended to be illustrative rather thanlimiting and are included herewith to facilitate the explanation of thepresent invention.

Referring generally to the figures, a breathing gas system according toan exemplary embodiment of the present invention is provided to heat,humidify and control patient respiratory gases. Warm, humidified gas isgenerated by the system and delivered to the user via a disposableand/or reusable humidification canister and an insulated delivery tubethat is attached to a user interface, such as a nasal cannula.

In an exemplary embodiment, heat and humidification may be providedthrough an exchange medium that is part of the humidification canister.The exemplary medium forms a semi-permeable membrane between a watersource (e.g., reservoir) and a humidification chamber within thehumidification canister. This medium acts as the interface to transferheat and molecular water vapor from the water source to the breathinggases by allowing heated molecules of water to transpire across themembrane into the breathing gases in the humidification chamber. Themedium may also act as a valve, restricting the amount of water that isvaporized. Optionally, the medium may be omitted.

The delivery tube and humidification canister provide pathways forheated air generated with heat from an internal heater, for example, tosurround or substantially surround the humidification chamber and gasdelivery tube, thereby reducing heat loss (and/or providing heat gain)as the gas makes its way through the system to the user, via a cannulaor a mask, for example. This arrangement minimizes water condensationand loss of beneficial heat and humidity before the breathing gas isdelivered to the user's airway and allows the temperature of thebreathing gas to be regulated independently from the addition of watervapor into the breathing gas.

In an exemplary embodiment, a system used to thermally insulate abreathing gas with insulating gas is disclosed. The insulating gas isprovided by a source, heated to a specified temperature, and thenprovided to a breathing gas delivery tube. The delivery tube includes aninner lumen through which the breathing gas is delivered from abreathing gas source to the user, and an outer jacket through which theinsulating gas travels such that the insulating gas insulates thebreathing gas as both the insulating gas and the breathing gas travelthrough the delivery tube. After the insulating gas has insulated thebreathing gas, the insulating gas may be exhausted to atmosphere.Alternatively, the insulating gas may be recirculated. Insulating gas isused to minimize heat loss of (and/or provide heat gain to) thebreathing gas as the breathing gas travels from the humidificationchamber to the user, thereby reducing rainout. Additionally, the use ofthe insulating gas allows adjustment to the temperature of the breathinggas without changing the water vapor content in the breathing gas,thereby adjusting relative humidity for added comfort.

Referring specifically to FIGS. 1 and 2, breathing gas system 100includes a base unit 102 configured to generate a first flow, orportion, of gas and a second flow, or portion, of gas. A humidificationcanister 104 is configured to be coupled to base unit 102.Humidification canister 104 may be a reusable and/or disposable unitthat is replaced after a specified period of time, such as after aprescribed number of days of use, a prescribed duration of use, or someother predetermined operating parameter.

A delivery tube assembly 106 is coupled to humidification canister 104(preferably releasably coupled). Delivery tube assembly 106 may be areusable and/or disposable unit that is replaced after a specifiedperiod, such as after a prescribed number of days of use, a prescribedduration of use, or some other predetermined operating parameter.

As shown if FIG. 2, a user device, such as, for example, a nasal cannula108, is configured to be releasably coupled to delivery tube assembly106. Exemplary nasal cannulae are disclosed in U.S. patent applicationSer. Nos. 11/940,793 and 11/940,867, which are both owned by theAssignee of the present invention and are incorporated herein byreference in their entireties.

Referring to FIGS. 2, 3 and 3A, base unit 102 includes a gas flow source113 and a fluid heater 198 configured to heat a fluid in humidificationcanister 104. Illustrated base unit 102 includes a gas flow source 113,such as, for example, a blower 112 configured to deliver an initial flowof gas and a flow divider 114 in fluid communication with an outlet 116of blower 112. As shown in FIG. 3A, flow divider 114 is configured todivide the initial flow of gas into a first flow of gas along a firstgas flow path 138 (indicated by alternating dots and dashes) and asecond flow of gas along a second gas flow path 144 (indicated by thedots).

In an exemplary embodiment, blower 112 may be a single source. Inanother exemplary embodiment, as will be described with reference toFIG. 28, blower 112 may include a plurality of sources.

An exemplary blower 112 may be a model number 939_3020_007 manufacturedby EBM Papst, Inc. of Farmington, Conn. Exemplary blower 112 may deliverair from outlet 116 of blower 112 at a delivery flow rate between about1 liter per minute and about 150 liters per minute.

Blower 112 provides an initial flow rate, which is divided by flowdivider 114 into a first flow of gas to be delivered to the user as abreathing gas at a desired delivery flow rate and a second flow of gasto be used as an insulating gas to insulate the breathing gas. While adesired delivery flow rate may be set, an actual flow rate of the firstflow of gas being delivered to the user may be greater than the deliveryflow rate during user inhalation and an actual flow rate of the firstflow of gas being delivered to the user may be less than the deliveryflow rate during user exhalation. Additionally, the initial flow ratemay remain generally constant, with the actual flow rate of the secondflow of gas decreasing as the flow rate of the first flow of gasincreases (e.g., due to patient inhalation), and with the actual flowrate of the second flow of gas increasing as the flow rate of the firstflow of gas decreases (e.g., due to patient exhalation).

Referring now to FIGS. 4 and 5, base unit 102 includes a case bottom 118that receives and retains blower 112 (not shown in FIGS. 4 and 5) andother components. Base unit 102 also includes a case top 120 that fitsover blower 112 and the components and attaches to case bottom 118. Casetop 120 also includes a receptacle 121 for receiving and holdinghumidification canister 104 in contact with fluid heater 198. Blower 112may be inserted into case bottom 118 and covered by case top 120.

Case bottom 118 includes a receptacle 122 for receiving and holdingblower 112. Case bottom 118 also includes a receptacle 124 for receivingand holding flow divider 114 (not shown in FIGS. 4 and 5) such that flowdivider 114 may be located between blower 112 and humidificationcanister 104 (not shown in FIGS. 4 and 5).

A filter cartridge 126 is releasably coupled to base unit 102. Filtercartridge 126 is used to filter air from atmosphere prior to enteringblower 112. Filter cartridge 126 removes airborne particulates that maybe harmful to the user if inhaled. Filter cartridge 126 may be snap fitto case bottom 118.

Case bottom 118 also includes a generally oval shaped opening 128therein and case top 120 includes a generally rectangular mating opening130 therein through which an electronic interface 132 (shownschematically if FIG. 9) extends. In an exemplary embodiment, interface132 may be a USB port that allows an operator, such as a physician or arespiratory therapist, to couple system 100 to an external device, suchas a computer (not shown), in order to program system 100 to meet theneeds of the particular user or to extract operating data from system100.

Interface 132 is electronically coupled to a printed circuit (PC) board134 (shown schematically in FIG. 9) or other electronic controller thatgoverns the operation of system 100. PC board 134 may be removablyinserted into a PC board slot 135 in case bottom 118.

Referring to FIGS. 3, 3A, and 6-8, flow divider 114 comprises a firstcompartment 136 including first gas flow path 138 for the first flow ofgas. First gas flow path 138 is configured to be coupled tohumidification canister 104 for humidification of the first flow of gas.First compartment 136 also includes a first compartment discharge port140.

Flow divider 114 further includes a second compartment 142 includingsecond gas flow path 144 for the second flow of gas. Second gas flowpath 144 is configured to receive the second flow of gas and to becoupled to humidification canister 104 to insulate at least a portion offirst gas flow path 138. Second compartment 142 also includes a secondcompartment discharge port 146 in line with first compartment dischargeport 140.

Illustrated flow divider 114 is constructed from a box 148 having anopen face 150. A rear wall 152 of box 148 includes a circular opening154 disposed proximate to the bottom of box 148. A rubber grommet 156 isdisposed within circular opening 154. Grommet 156 is coupled to outlet116 of blower 112 to receive gas generated by blower 112.

A cover 158 is disposed over open face 150 of box 148, forming agenerally closed compartment. Cover 158 includes second compartmentdischarge port 146 disposed proximate to the top of cover 158. A rubberinlet grommet 161 is disposed within second compartment discharge port146. Inlet grommet 161 is coupled to humidification canister 104 todischarge the gas flow generated by blower 112 from flow divider 114 tohumidification canister 104.

A back-up plate 162 is disposed within box 148 to separate box 148 intofirst compartment 136 and second compartment 142. Back-up plate 162includes first compartment discharge port 140 disposed proximate to thetop of back-up plate 162, co-axially aligned with second compartmentdischarge port 146 in cover 158. A rubber back-up plate grommet 170 isdisposed within first compartment discharge port 140 of back-up plate162.

Back-up plate 162 also includes a generally elongated opening 172 in thebottom thereof to provide fluid communication between first compartment136 and second compartment 142. Additionally, back-up plate 162 furtherincludes raised ridges 174 in a plurality of locations on secondcompartment side of flow divider 114. As shown in FIG. 6, four (4)raised ridges 174 are shown, although those skilled in the art willrecognize that more or less than four raised ridges 174 may be used.Raised ridges 174 are used to locate an insulator board 176 on back-upplate 162 between upper and lower raised ridges 174.

An insulating gas heater 180 is disposed within second compartment 142and is adapted to heat the second flow of gas. Insulating gas heater 180is attached to insulator board 176 in second compartment 142. Anexemplary insulating gas heater 180 is a heating plate having aplurality of elongated ribs 182 extending therefrom to dissipate heatgenerated from insulating gas heater 180 to surrounding gas flowingthrough second compartment 142. Insulating gas heater 180 may beconstructed from aluminum or other suitable heat conductive material.Insulating gas heater 180 is electrically coupled to PC board 134 (shownin FIG. 9) such that PC board 134 controls operation of insulating gasheater 180.

Referring to FIG. 3A, in use, blower 112 directs air into flow divider114, where the air is divided into first gas flow path 138 in firstcompartment 136 and second gas flow path 144 in second compartment 142.Gas within second gas flow path 144 is heated by insulating gas heater180. Second gas flow path 144, having been heated by insulating gasheater 180, surrounds gas within first gas flow path 144 as the firstgas flow passes from first compartment 136, through second compartment142 and discharge port 140, and out of flow divider 114 tohumidification canister 104.

Referring back to FIG. 5 a canister latch 194 releasably coupleshumidification canister 104 to base unit 102. Canister latch 194 isgenerally arcuate in shape and includes connectors 196 at each end forcoupling to case top 120. In an alternative embodiment, latch 194 may beomitted, and humidification canister 104 may be releasably coupled tobase unit 102 via a frictional engagement.

Referring back to FIG. 2, fluid heater 198 is configured to provide heatto humidification canister 104 (e.g., via conduction), which heats thefluid for heating and humidifying the first flow of gas inhumidification canister 104. Fluid heater 198 is located on case top120. Fluid heater 198 may be a conventional plate heater (which mateswith a corresponding plate of humidification canister 104). Fluid heater198 is electrically coupled to PC board 134 (shown in FIG. 9) such thatPC board 134 controls operation of fluid heater 198.

FIG. 9 depicts an exemplary control circuit 200 for controlling system100 (FIGS. 1 and 2). Illustrated control circuit 200 is formed on PCboard 134, which is removably inserted in slot 135 in case bottom 118(shown in FIG. 4). Control circuit 200 provides control for threeprimary controllers. A first controller 202 is operatively coupled tohumidifier heater 198 and, under control of control circuit 200,controls the temperature of humidifier heater 198 and regulates thetemperature of the first flow of gas based on a delivery flow rate ofthe first flow of gas. A second controller 204, under control of controlcircuit 200, controls temperature of insulating gas heater 180, and athird controller 206, under control of control circuit 200, isconfigured to operate blower 112 to deliver the first flow of gas at adelivery flow rate. Control circuit 200 is accessible by an externalcomputer (not shown) via a communications port, such as interface 132.

Interface 132 provides for adjustment of controllers 202, 204, 206,under control of control circuit 200, through the full range ofoperation of humidifier heater 198, insulating gas heater 180, andblower 112, respectively. An exemplary use of interface 132 is withsystem 100 in a sleep lab, where multiple users may be “titrated” usingsystem 100 during a sleep study to determine ideal system settings for aparticular user. Interface 132 may allow operational information for aparticular user to be downloaded from an outside device, such as a USBdevice (not shown), to control circuit 200.

Electrically, this embodiment of system 100 operates within the range of100-240 VAC and 50-60 Hz. The maximum power consumption is desirablyless than about 60 Watts. Power inlet 208 includes a removable 3-meterlong hospital grade power cord.

Control circuit 200 uses thermistors to sense temperature at variouslocations within system 100. Exemplary thermistors are rated at 15 KΩ @+25 C. A humidifier thermistor 210 measures the temperature ofhumidifier heater 198 to an accuracy of about +/−0.5° C. An air heaterthermistor 212 measures the temperature of insulating gas heater 180 toan accuracy of about +/−0.5° C.

An AC power supply 208 provides AC power to system 100, includingcontrollers 202, 204. In an exemplary embodiment, a 24 VDC power supply214 capable of about 1 amp is used to power third controller 206.Alternatively, other power supplies, such as, for example, 12V at 2amps, may be used.

Control circuit 200 provides speed control of blower 112 over anadjustable range of 0 to 100%, with a precision of about 1% +/−0.5%.Power supply 214 is also coupled to a Low Voltage Power Supply (LVPS)216 that reduces the voltage to control circuit 200.

In an exemplary embodiment, control circuit gradually increases speed(ramp-up) to set blower speed over a pre-determined period of time, suchas, for example, twenty minutes. In an exemplary embodiment, every fiveminutes during ramp-up, blower speed will increase 25% until blower 112reaches its set speed. Control circuit 200 includes a power button 218that operates system 100. Power button 218 may be pressed a first timeto power up system 100. If power button 218 is pressed a second time,the ramp function may be de-activated and blower 112 immediately goes tothe speed set on control circuit 200.

After use, power button 218 may be pressed to turn off system 100. Whensystem 100 is turned off, humidifier heater 198 turns off, but blower112 and insulating gas heater 180 continue to run for a predeterminedperiod of time, such as, for example, 1 minute, before turning off.Control circuit 200 may be configured to deactivate humidifier heater198 if humidification canister 104 is not installed

An optional ambient temperature sensor 220 monitors the ambienttemperature around system 100 and feeds the recorded temperature tocontrol circuit 200. Control circuit 200 may regulate insulating gastemperature by adjusting insulating gas heater 180 based on ambienttemperature to maintain an approximate outlet temperature, such as about37 degrees Celsius. Optionally, water level sensor 224 monitors thelevel of humidification fluid “F” in fluid supply reservoir 232 andfeeds the recorded level to control circuit 200.

Control circuit 200 is configured to shutdown system 100 ifpredetermined parameters fall outside of a specified range. In anexemplary embodiment, such parameters may include, but are notnecessarily limited to, breathing gas temperature (greater than 1 degreeC. above set point), blower malfunction, insulating gas heater 180(greater than 5 degrees C. above set point, and humidifier heater 198(greater than 5 degrees C. above set point).

In an exemplary embodiment, insulating gas heater 180 and fluid heater198 are regulated by control circuit 200 based on a set flow rate ofblower 112, a comfort setting (described below), and, optionally, anambient temperature value recorded by temperature sensor 220. Inembodiments where ambient temperature is not employed, a look-up tablemay be used by control circuit 200 to select appropriate values fordriving heater driver 204 for insulating gas heater 180 and heaterdriver 202 for fluid heater 198 based on the set rate of blower 112 andthe comfort setting. In embodiments where ambient temperature isemployed, separate look-up tables may be provided for different ambienttemperature ranges. In accordance with this embodiment, a particularlook-up table may be selected based on an ambient temperature value and,then, that look-up table may be used by control circuit 200 to selectappropriate values for driving heater driver 204 for insulating gasheater 180 and heater driver 202 for fluid heater 198 based on the setrate of blower 112 and the comfort setting.

The use of an insulating gas heater 180 and a fluid heater 198 enablesthe temperature and the fluid content of the breathing gas to beindependently regulated, thereby controlling relative humidity. Forexample, the setting of the fluid heater 198 may be used to regulate theamount of fluid in the breathing gas and the setting of the insulatinggas heater 180 may be used to regulate the temperature of the breathinggas being delivered to the user. Relative humidity can be adjusted byincreasing/decreasing the fluid content while holding the temperature ofthe breathing gas constant, maintaining the fluid content whileincreasing/decreasing the temperature, or increasing/decreasing thefluid content while increasing/decreasing the temperature. Suitablecontrol logic and look-up tables to perform these tasks will be readilyunderstood by one skilled in the art from the description herein.

In an exemplary embodiment, a physician, respiratory therapist, or othermedical professional sets the flow rate of blower 112 prior to use ofsystem 100. The user may then select from a plurality of comfortsettings such as, for example, a “cool” setting (e.g., a breathing gastemperature to be delivered to user between about 30 and about 33degrees Celsius with a relative humidity of between about 80% and about100%), a “medium” setting (e.g., a breathing gas temperature to bedelivered to user between about 33 and about 35 degrees Celsius with arelative humidity of between about 80% and about 100%), or a “warm”setting (e.g., a breathing gas temperature to be delivered to userbetween about 35 and about 37 degrees Celsius with a relative humidityof between about 80% and about 100%). Pushbutton 218 may includeseparate up and down buttons (not shown) that may be pressed to select adesired setting from among the plurality of available comfort settings.

Referring now to FIGS. 2 and 10-15A, humidification canister 104 isconfigured to heat and humidify the first flow, or portion, of the gasgenerated by blower 112 (not shown in FIGS. 10-15A). Humidificationcanister 104 includes a humidification chamber 230 that heats andhumidifies the first flow, or breathing, gas, a fluid supply reservoir232 that provides fluid “F”, typically in the form of water, to humidifythe breathing gas. Fluid supply reservoir 232 is operatively coupled tohumidification chamber 230 to transmit water to humidification chamber230 where the water is vaporized. Humidification canister 104 furtherincludes an insulation chamber 233 that uses the second flow of the gas(insulating gas) to at least partially surround and insulate thebreathing gas flowing through the first gas flow path of humidificationcanister 104, including humidification chamber 230. Second gas flow path144 extends through insulation chamber 233 and provides fluidcommunication between blower 112 and delivery tube assembly 106.

Humidification canister 104 is operatively coupled to blower 112 toreceive the first flow of gas along first gas flow path 138 and toreceive the second flow of gas along second gas flow path 144. An inletconnector 234 includes a breathing gas lumen 235 that is in fluidcommunication with first compartment 136 (shown in FIG. 6) and extendsfrom inlet grommet 161 in front cover 158, through second compartment142, through back-up plate grommet 170 in back-up plate 162 to firstcompartment discharge port 140 such that first gas flow path 138 passesfrom first compartment 136 and into and through second compartment 142.An insulating gas lumen 236 extends through inlet grommet 161 in frontcover 158 and is coaxially disposed around breathing gas lumen 235downstream of flow divider 114 such that first gas flow path 138 andsecond gas flow path 144 are generally coaxial.

In an exemplary embodiment, breathing gas lumen 235 is also in fluidcommunication with a humidifier inlet elbow 237 that directs thebreathing gas to a humidification chamber 230. Humidifier inlet elbow237 is constructed from an outer elbow portion 238 and an inner elbowportion 239. Outer elbow portion 238 is part of a lid top 240 ofhumidification chamber 230 and inner elbow portion 239 is part of a lidbottom 241 of humidification chamber 230. A volume between lid top 240and lid bottom 241 defines an insulating space 242 in fluidcommunication with insulating gas lumen 236 and insulating chamber 233.

Humidifier elbow 237 is coupled to an inlet baffle tube 243, whichextends through an opening 232 a in fluid supply reservoir 232 (shown inFIG. 14A). Inlet baffle tube 243 discharges into a humidification dome244. Humidification dome 244 is generally conical in shape.Humidification dome 244 is removably coupled to bottom of fluid supplyreservoir 232 such that humidification dome 244 may be removed fromfluid supply reservoir 232 for replacement and/or cleaning.

A discharge end of inlet baffle tube 243 includes a baffle 245 thatredirects breathing gas from a generally vertical downward direction toa generally horizontal direction. Referring to FIGS. 12 and 12A, a flatsheet membrane in the form of filter media 246 is disposed belowhumidification dome 244 and, together with humidification dome 244,filter media 246 defines humidification chamber 230. Filter media 246 isa generally circular piece of polytetrafluoroethylene (PTFE), which hasan arcuate cutout 247 along its perimeter. The redirection of thebreathing gas by baffle 245 may prevent the breathing gas from impingingdirectly onto the top surface of filter media 246, which may reduce wearof filter media 246. Additionally, the redirection of the breathing gasmay improve the residence time of the breathing gas withinhumidification chamber 230, improving the heating and humidification ofthe breathing gas.

As shown in FIG. 11, filter media 246 is disposed in the path of fluid“F” between fluid supply reservoir 232 and humidification chamber 230,which is in first gas flow path 138. While fluid supply reservoir 232 isconfigured to hold fluid “F” in fluid communication with first gas flowpath 138, filter media 246 restricts passage of fluid “F” from fluidsupply reservoir 232 into first gas flow path 138 to introduce theproper amount of fluid “F” to humidification chamber 230.

Filter media 246 is disposed within a media holder 248, which is shownin detail in FIGS. 13 and 13A. Media holder 248 includes an arcuateprotrusion 249 sized to match arcuate cutout 247 in media filter 246.Media holder 248 includes a plurality of struts 250 that support filtermedia 246. Media holder 248 also includes an opening 251 proximate toarcuate protrusion 249.

Referring back to FIG. 11, a retaining ring 252 may be disposed overfilter media 246 to retain filter media 246 on media holder 248.Although not shown, in an alternative embodiment, filter media 246 maybe insert molded into a media holder, eliminating the need for retainingring 252.

An annular tin gasket 253 is disposed under media holder 248. A circulartin heater plate 254 is disposed below gasket 253. When humidificationcanister 104 is coupled to base unit 102, heater plate 254 is disposedon top of fluid heater 198 to facilitate transfer of heat from fluidheater 198 to heater plate 254, which heats fluid that flowed from fluidsupply reservoir 232 onto heater plate 254.

Referring now to FIGS. 2, 11, 14, and 14A, fluid supply reservoir 232includes a drainage nipple 255 that extends from the bottom of fluidsupply reservoir 232 and through opening 251 in media holder 248 toprovide fluid communication from the interior of fluid supply reservoir232 to the upper surface of heater plate 254. Optionally, although notshown, a valve, such as a Schrader valve, may be used to prevent fluidfrom flowing through drainage nipple 255 when fluid supply reservoir 232is not coupled to base unit 102, but to open the valve when fluid supplyreservoir 232 is coupled to base unit 102, to allow fluid flow fromfluid supply reservoir 232 to heater plate 254. This valve prevents lossof fluid from fluid supply reservoir 232 when fluid supply reservoir 232is not coupled to base unit 102, but allows for fluid communicationbetween fluid supply reservoir 232 and humidification chamber 230 whenfluid supply reservoir 232 is coupled to base unit 102.

Referring to FIGS. 2 and 11, an outlet baffle tube 256 is coupled tohumidification dome 244 and extends from humidification chamber 230,through an opening 232 b in fluid supply reservoir 232 (shown in FIG.14A), to an outlet elbow 257. Outlet elbow 257 is constructed from anouter elbow portion 258 and an inner elbow portion 259. Outer elbowportion 258 is part of lid top 240 of humidification chamber 230 andinner elbow portion 259 is part of lid bottom 241 of humidificationchamber 230.

Outlet elbow 257 is coupled to an outlet connector 260 which includes abreathing gas lumen 261 that is in fluid communication with outletbaffle tube 256 and an insulating gas lumen 262, coaxially disposedaround breathing gas lumen 261, that is in fluid communication withinsulation chamber 233 and insulating space 242. An exterior ofillustrated outlet connector 260 includes a pair of diametricallyopposed locking nubs 263 extending outwardly therefrom.

Referring to FIGS. 15 and 15A, lid bottom 241 includes an opening 264therethrough. Opening 264 allows insulating space 242 to be in fluidcommunication with fluid “F” in fluid supply reservoir 232, providing apressurization path between second gas flow path 144 and fluid supplyreservoir 232 to pressurize fluid supply reservoir 232 with the secondflow of gas.

Lid bottom 241 also includes a refill opening 265 that is in fluidcommunication with fluid supply reservoir 232 such that a cover (notshown) can be removed from refill opening 265 so that fluid can be addedthrough refill opening 265 to replenish fluid “F” in fluid supplyreservoir 232.

First gas flow path 138 extends through humidification canister 104 frombreathing gas lumen 235, through humidifier inlet elbow 237, down inletbaffle tube 243, to humidification chamber 230 where breathing gas infirst gas flow path 138 is heated and humidified. The heated andhumidified breathing gas exits humidification chamber 230 through outletbaffle tube 256, through outlet elbow 257 to breathing gas lumen 261 fordischarge from humidification canister 104.

In an alternative embodiment, as shown in the schematic drawing of FIG.16, second gas flow path 144 may bypass humidification canister 104 suchthat second gas flow path 144 extends directly from flow divider 114 todelivery tube assembly 106.

While exemplary embodiments of a humidification canister 104 are shown,those skilled in the art will recognize that other embodiments ofhumidification canisters from the description herein are contemplated bythe present invention and such embodiments are considered within thescope of the present invention.

Although air/gas is used to insulate the breathing gas in the exemplaryembodiment, it is contemplated that water/liquid may be used forinsulating/heating breathing gas in addition to or instead of air/gas.

Delivery tube assembly 106 is used to deliver the breathing gas fromhumidification canister 104 to the user. Referring now to FIGS. 2 and17-26, illustrated delivery tube assembly 106 includes a multilumendelivery tube having a first, or inner, lumen 270 and a second, or outerlumen 276. Lumen 270 has an upstream portion 272 in fluid communicationwith humidification chamber 230 and with first gas flow path 138 toreceive humidified breathing gas from humidification canister 104 and adownstream portion 274 configured to deliver the humidified breathinggas to nasal cannula 108 or other breathing device. First lumen 270 isconfigured to deliver the breathing gas from upstream portion 272 todownstream portion 274.

Outer lumen 276 is adjacent to and at least partially surrounds innerlumen 270 such that inner lumen 270 is disposed within outer lumen 276.Outer lumen 276 is in fluid communication with insulation chamber 233and with second gas flow path 144 to receive the second flow of gas.Outer lumen 276 is configured to pass the second flow, or insulating,gas around inner lumen 270. Outer lumen 276 is configured for couplingto humidification canister 104 to receive the insulating gas and isadapted to transmit the insulating gas from humidification canister 104along the length of inner lumen 270 and to discharge the insulating gasto atmosphere.

In an exemplary embodiment, inner lumen 270 may be a tube, such as ModelNo. Type 777, manufactured by Hi-Tech Medical of Georgetown, Mass.,having an inner diameter of about 10 mm. Inner lumen 270 may have alength of about 180 cm. Upstream portion 272 and downstream portion 274of inner lumen 270, as well as an inner surface of inner lumen 270, maybe generally smooth. An outer surface 278 of inner lumen 270 betweenupstream end 272 and downstream end 274 may be corrugated. Suchcorrugation reduces the likelihood of kinking inner lumen 270 and alsoprovides for coupling of spacers to the exterior of inner lumen 270.

In an exemplary embodiment, outer lumen 276 may be a tube, such as ModelNo. Type 555, manufactured by Hi-Tech Medical of Georgetown, Mass.having an inner diameter of about 19 mm. Outer lumen 276 may have alength of about 180 cm. Outer lumen 276 may have a generally smoothupstream end 280 and inner surface, and a corrugated outer surface 282that extends downstream of upstream end 280. Such corrugation reducesthe likelihood of kinking cannula 108.

Referring to FIGS. 18-20, a plurality of spacers 284 are disposed withinouter lumen 276 such that inner lumen 270 is generally centered withinouter lumen 276. Spacers 284 may be spaced about 30 cm apart along thecorrugated portion of inner lumen 270. Each spacer 284 includes anarcuate frame 286 extending in a plane and a plurality of longitudinalstruts 288 extending generally perpendicular to the plane. Arcuate frame286 is sized to fit in a groove between adjacent ridges of the exteriorof corrugated inner lumen 270. Arcuate frame 286 extends in an arc ofover 180 degrees such that arcuate frame 286 can be snapped over groove.In an exemplary embodiment, arcuate frame 286 extends in an arc of about240 degrees. Longitudinal struts 288 engage interior wall of outer lumen276.

Referring back to FIG. 17-18 and to FIGS. 21-23, an upstream portion 290of delivery tube assembly 106 includes a twist lock connector 292 thatis adapted to releasably couple delivery tube assembly 106 tohumidification canister 104. In an exemplary embodiment, twist lockconnector 292 may be constructed from high density polyethylene (HDPE),polypropylene, or other suitable material. Twist lock connector 292includes a base portion 294 having a pair of diametrically opposed slots296, with a first slot portion 297 extending toward downstream portion298 (shown in FIG. 17) of delivery tube assembly 106. A second slotportion 300 of each of slots 296 extends transversely to first slotportion 297. Locking nubs 263 from humidification canister 104 (shown inFIG. 11) are sized to fit into first slot portion 297 as twist lockconnector 292 is advanced over outlet connector 260. When twist lockconnector 292 is advanced such that locking nubs 263 are at theintersection between first slot portion 297 and second slot portion 300,twist lock connector 292 is rotated such that locking nubs are advancedto the closed end of second slot portion 300, thereby releasablycoupling delivery tube assembly 106 to humidification canister 104.

Twist lock connector 292 further includes an inner lumen portion 302that extends downstream from base portion 294. Inner lumen portion 302is coupled to base portion 294 via a pair of diametrically opposedspacers 304. Twist lock inner lumen portion 302 is coupled to upstreamend 272 of inner lumen 270.

Twist lock connector 292 also includes an outer lumen portion 306 thatextends downstream from base portion 294. Outer lumen portion 306 iscoupled to an outer perimeter of base portion 294. Twist lock outerlumen portion 306 is coupled to upstream end 280 of outer lumen 276.

Referring to FIGS. 17, 18, and 24-26, delivery tube assembly 106 furtherincludes a flow diverter assembly 310 coupled to downstream portion 274of inner lumen 270. Diverter assembly 310 is adapted to divert theinsulating gas flowing through outer lumen 276 in a direction away fromdownstream portion 274 of inner lumen 270 to atmosphere. Diverterassembly 310 is swivelly coupled to downstream portion 274 of the innerlumen 270 to reduce potential kinking of cannula 108 during use.

FIGS. 24-26 illustrate an exemplary flow diverter assembly 310. Flowdiverter assembly 310 includes an input portion 312, a discharge portion314, and a diverter portion 316 disposed between input portion 312 anddischarge portion 314. Fins 318 space diverter portion 316 from outerlumen 276. Breathing gas, shown in FIGS. 24 and 26 as arrow A, flowsfrom inner lumen 270 (shown in FIG. 26), through input portion 312 anddischarge portion 314 to nasal cannula 180 (not shown in FIG. 24).Insulating gas, shown in FIG. 24 as arrow B, flows from outer lumen 276,through input portion 312 to diverter portion 316, where the insulatinggas is diverted (e.g. about 180 degrees) and discharged from diverterassembly 310 and away from the user.

Using air/gas instead of water to insulate the breathing gases andexhausting the insulating gas to atmosphere eliminates the need for aheating fluid recirculation system, reduces the potential for leaks andbacterial contamination, and enables a lightweight delivery tube to beused in the system.

Referring to FIGS. 1-26 and the flow chart 500 of FIG. 27, an exemplaryoperation of system 100 is as follows. In STEP 502 the speed of blower112 is set. In an exemplary embodiment, a professional, such as aphysician or a respiratory therapist, determines a desired flow rate ofbreathing gas to be administered to the user, and adjusts controlcircuit 200 to control third controller 206 to set a speed of blower112. By setting third controller 206 to the desired setting, a rate ofan initial flow of gas, which is the total of a rate of the first flowof gas (the breathing gas) and a rate of the second flow of gas (theinsulating gas), is set. In an alternative exemplary embodiment, aperson receiving the therapy may set the flow rate.

In STEP 504, blower 112 is started. In an exemplary embodiment, the userpresses power button 218, resulting in control circuit 200 startingblower 112, as well as transmitting signals to first controller 202 andsecond controller 204 to operate insulating gas heater 180 andhumidifier heater 198. The starting of blower 112 generates an initialflow of gas. In STEP 506 the initial flow of gas is divided into a firstflow of gas and a second flow of gas. In an exemplary embodiment, theinitial flow of gas flows into flow divider 114, where the initial flowof gas is divided into the first flow of gas in first compartment 136for breathing and the second flow of gas in second compartment 142 forinsulating the first flow of gas. In STEP 508, the first flow of gasflows along first gas flow path 138, while in STEP 510, the second flowof gas flows along second gas flow path 144. As shown in the flow chart500, the breathing gas and the insulating gas flow in generally parallelpaths.

In STEP 512, the second flow of gas is heated. In an exemplaryembodiment, the second flow of gas is heated by insulating gas heater180 as the second flow of gas flows through second compartment 142. Inan exemplary embodiment, the second flow of gas is heated for use ininsulating at least a portion of the first flow of gas in the first gasflow path 138.

In STEP 514, the breathing gas flow is directed along first gas flowpath 138. In an exemplary embodiment, first gas flow path 138 includeshumidification chamber 230. The flow of the breathing gas is directedthrough breathing gas lumen 235, which is the inlet to humidificationchamber inlet 230.

In STEP 516, humidification fluid is heated. In an exemplary embodiment,as the breathing gas flows along first gas flow path 138 throughhumidification chamber 230, humidifier heater plate 254 heats fluid “F”that has flowed from fluid supply reservoir 232 to top of heater plate254. The heated fluid passes through filter media 246 and into first gasflow path 138 within humidification chamber 230, where the heated fluidvaporizes. The vaporized fluid heats and humidifies the first flow ofgas in first gas flow path 138. The flow of the now heated andhumidified breathing gas is then directed through breathing gas lumen261, which is the outlet of humidification chamber 230.

In STEP 518, the flow of the insulating gas is directed along second gasflow path 144. In an exemplary embodiment, second gas flow path 144includes insulating chamber 233, which at least partially surroundshumidification chamber 230. The flow of the insulating gas is directedthrough insulating gas lumen 236, which is the inlet to insulatingchamber 233. The flow of the insulating gas is directed throughinsulating gas lumen 262, which is the outlet from insulating chamber233. Throughout STEP 518, the insulating gas provides insulation to andregulates the temperature of the breathing gas (e.g., by minimizing thetemperature drop of the breathing gas).

Further, humidification fluid “F” within fluid supply reservoir 232 ispressurized by the insulating gas within humidification canister 104. InSTEP 520, humidification fluid is provided. In an exemplary embodiment,the supply of the humidification fluid “F” is provided withinhumidification canister 104 to humidify the breathing gas. In STEP 522,fluid communication is also provided between second gas flow path 144and supply of humidification fluid “F.” In an exemplary embodiment, thefluid communication is provided via opening 263 in lid bottom 241 ofhumidification canister 104 such that, in STEP 524, humidification fluid“F” is pressurized with the insulating gas. In STEP 526, fluid “F” isheated. In an exemplary embodiment, fluid “F” is heated with humidifierheater 198, which is transmitted through filter media 246 and into firstgas flow path 138. In STEP 516, the breathing gas is humidified. In anexemplary embodiment, the breathing gas is humidified in humidificationchamber 230. In STEP 528, the insulating gas insulates the breathinggas. In an exemplary embodiment, the insulating gas in insulatingchamber 233 insulates the breathing gas in humidification chamber 230.

In STEP 530 the heated and humidified breathing gas is discharged fromhumidification canister 104. In an exemplary embodiment, the heated andhumidified breathing gas is directed through breathing gas lumen 261 inhumidification canister 104 and then, in STEP 532, the heated andhumidified breathing gas is discharged into delivery tube assembly 106.In STEP 534, the heated and humidified breathing gas flows throughdelivery tube assembly 106. In an exemplary embodiment, the heated andhumidified breathing gas flows through first, or inner, lumen 270 in afirst direction. from upstream portion 272 to downstream portion 274 ofinner lumen 270. The breathing gas is discharged from the downstream endof delivery tube assembly 106 into breathing device 108 for inhalationby the user.

In STEP 536, the insulating gas is discharged from humidificationcanister 104. In an exemplary embodiment, the insulating gas is directedthrough insulating gas lumen 262 and out of humidification canister 104.In STEP 538, the breathing gas is received in the upstream end ofdelivery tube assembly 106. In STEP 540, the insulating gas at leastpartially insulates the breathing gas. In an exemplary embodiment, theinsulating gas flows through second, or outer, lumen 276, wherein theinsulating gas at least partially insulates the heated and humidifiedbreathing gas. The insulating gas also flows in the first direction fromupstream to downstream. In an exemplary embodiment, the insulating gasis discharged to atmosphere from downstream end of delivery tubeassembly 106 through diverter assembly 310, which diverts the insulatinggas away from the user.

In STEP 542, after use, system 100 is turned off. In an exemplaryembodiment, when the user presses power button 218 to turn off system100, humidifier heater 198 turns off but blower 112 and insulatingheater 180 continue to run for a predetermined period of time, such as,for example, 1 minute, before turning off. Additionally, control circuit200 may be configured to deactivate humidifier heater 198 ifhumidification canister 104 is not installed

Referring to FIG. 27 dashed lines connecting STEPS 514-518, 516-528,530-536, 532-538, and 524-538 indicate locations along first gas flowpath 138 where the breathing gas is or may be insulated by theinsulating gas flowing along second gas flow path 144.

Ambient temperature sensor 220 monitors the ambient temperature aroundsystem 100 and feeds the recorded temperature to control circuit 200.Control circuit 200 regulates insulating gas temperature by adjustingthe insulating heater 180 to maintain an approximate outlet temperatureof the insulating gas, such as about 37 degrees Celsius.

While an exemplary embodiment of a breathing assistance system 100 andits operation are described above, the present invention may encompassother embodiments as well. As discussed above, gas flow source maycomprise a plurality of sources. In the exemplary embodiment of abreathing gas delivery system 700 shown in FIG. 28, a first source ofgas 702 may be a compressed gas, such as oxygen. A second source of gas704 may be air, generated by a blower. Alternatively, both first sourceof gas 702 and second source of gas 704 may be blowers. Also, both gassources 702, 704 may be compressed gas sources such as oxygen and/or airfrom a high pressure source.

Additionally, in an alternative embodiment of a breathing system 709shown schematically in FIG. 29, an auxiliary gas port 710 may extendfrom an upstream end 712 of an inner lumen 714 to facilitate connectionof a pressurized gas source, such as oxygen, for inhalation by a userthrough nasal cannula 108.

Further, an alternative embodiment of a delivery tube assembly 600,shown in cross section in FIG. 30, uses a plurality of fins 601 formedwith or coupled to the exterior of inner lumen 602 to space inner lumen602 generally coaxially within an outer lumen 604.

Still another alternative embodiment of a delivery tube assembly 800 maybe used instead of delivery tube assembly 106. As shown in cross sectionin FIG. 31 and schematically in FIG. 32, first lumen 802 may begenerally centrally disposed within delivery tube assembly 800, with asecond lumen 804 comprising a first lumen portion 806 extendingapproximately the length of first lumen 802, and a second lumen portion808 extending approximately the length of first lumen 802. First andsecond lumen portions 806, 808 surround first lumen 802. First andsecond lumen portions 806, 808 may be generally “C-shaped” in crosssection. A septum 810 separates first lumen 802 from each of first andsecond lumen portions 806, 808. At a downstream end 814 of assembly 800,first lumen portion 806 and second lumen portion 808 are in fluidcommunication with each other and at an upstream end 814 of assembly800, first lumen portion 806 and second lumen portion 808 are not influid communication with each other.

In operation, breathing gas enters first lumen 802 from humidificationcanister 104 and travels through the length of first lumen 802, wherethe breathing gas is discharged to nasal cannula 108. Insulating gasenters first lumen portion 806 from humidification canister 104 atupstream end 816 of assembly 800 and travels through first lumen portion806 to downstream end 814 of assembly 800. The insulating gas thenenters second lumen portion 808 and travels through second lumen portion808 to upstream end 816 of assembly 800, where the insulating gasdischarges to atmosphere.

In yet another alternative embodiment of a delivery tube assembly 900,shown schematically in FIG. 33, delivery tube assembly 900 has a similarcross section to delivery tube assembly 800 shown in FIG. 31 and mayinclude a first, inner lumen 902 that has an upstream end 904 configuredto couple to humidification canister 104 and a downstream end 906configured to couple to nasal cannula 108 such that the breathing gasflows through first lumen 902 from upstream end 904 to downstream end906.

Delivery tube assembly 900 also includes a second lumen 908 having afirst lumen portion 910 and a second lumen portion 912 which, together,generally surround first lumen 902. First lumen portion 910 and secondlumen portion 912 may be generally “C-shaped” in cross section (similarto lumen portions 806, 808 shown in FIG. 31. Delivery tube assembly 900includes a diverter assembly, such as diverter assembly 310 illustratedin FIGS. 17, 18, and 24-26 and described above, that is coupled todownstream end 906 first lumen 902. Diverter assembly 319 redirects theinsulating gas flowing through first lumen portion 910 and a secondlumen portion 912 away from the user and to atmosphere.

Although the invention is illustrated and described herein withreference to specific embodiments, the invention is not intended to belimited to the details shown. Rather, various modifications may be madein the details within the scope and range of equivalents of the claimsand without departing from the invention.

What is claimed:
 1. A humidification system for increasing residencetime of a breathing gas within a humidification chamber so as to provideheated and humidified breathing gas to a patient through a nasalcannula, the system comprising: a humidification canister having: a heatconducting base, a liquid reservoir configured to hold a liquid, ahumidification chamber having a curved inner wall positioned within theliquid reservoir, a gas inflow conduit configured to convey a flow ofbreathing gas into the humidification chamber, a gas outflow conduitconfigured to convey breathing gas away from the humidification chamberafter being humidified within the chamber, and a first baffle tubehaving an inlet section and a discharge section, the inlet sectioninterfacing with the gas inflow conduit so as to receive the flow ofbreathing gas in a first generally horizontal direction of flow anddirect the received flow of breathing gas in a second, generallyvertical direction of flow, the discharge section having an outletbaffle and being positioned so as to re-direct the gas from the verticaldirection of flow to a generally downward direction of flow whendischarging from the outlet baffle into the humidification chamber; anda base unit comprising: a housing, a fluid heater disposed on a surfaceof the housing and configured to transfer heat to the heat conductingbase of the humidification canister, a blower enclosed within thehousing and configured to provide the flow of breathing gas through thegas inflow conduit, and a receptacle configured to releasably couple thehumidification canister to the base unit, the receptacle sized andshaped to accommodate the humidification canister; wherein thereceptacle is configured to position the humidification canister abovethe fluid heater and to align the gas inflow conduit with the base unitto provide breathing gas to the humidification chamber.
 2. Thehumidification system of claim 1, wherein the inlet section of the firstbaffle tube has a first cross sectional area, and the discharge sectionhas a second cross-sectional area, and wherein the first cross-sectionalarea is smaller than the second cross-sectional area.
 3. Thehumidification system of claim 1, wherein the discharge section has asecond cross-sectional area and at least one section of the first baffletube between the inlet section and the discharge section has a thirdcross-sectional area, and wherein the third cross-sectional area issmaller than the second cross-sectional area.
 4. The humidificationsystem of claim 1, wherein the discharge section of the first baffletube comprises an upper surface and a lower surface, and wherein one ofthe upper and lower surfaces is horizontal within the canister and theother of the upper and lower surfaces has a downward slope with respectto the horizontal surface.
 5. The humidification system of claim 4,wherein the upper and lower surfaces are configured such that a velocityvector of breathing gas flowing between the upper and lower surfaces hasboth a horizontal and a vertical component, and the horizontal componentis greater than the vertical component.
 6. The humidification system ofclaim 5, wherein the upper and lower surfaces are configured such thatthe flow of breathing gas between the upper surface and the lowersurface is directed at a downward angle between the horizontal surfaceand the downward sloped surface.
 7. The humidification system of claim6, wherein the upper surface and the lower surface direct the flow ofbreathing gas downward toward the liquid reservoir to maximize aresidence time of the flow of breathing gas within the humidificationchamber.
 8. The humidification system of claim 7, further comprising agas contact surface between the discharge section and an upper surfaceof the liquid reservoir.
 9. The humidification system of claim 8,wherein the gas contact surface is a membrane.
 10. The humidificationsystem of claim 7, wherein the upper surface has a downward slope. 11.The humidification system of claim 4, further comprising a second baffletube coupling the humidification chamber to the gas outflow conduit. 12.The humidification system of claim 11, wherein the second baffle tubehas an inlet opening configured to receive heated and humidifiedbreathing gas from the humidification chamber in a generally horizontaldirection and an inlet baffle configured to receive the heated andhumidified breathing gas from the inlet opening and discharge the heatedand humidified gas toward the gas outflow conduit in a generallyvertical direction.
 13. The humidification system of claim 12,comprising first and second elbows positioned respectively in the firstbaffle tube and second baffle tube.
 14. The humidification system ofclaim 4, wherein the upper surface comprises a top of the humidificationchamber positioned vertically above the outlet baffle.
 15. Thehumidification system of claim 14, wherein the outlet baffle directs theflow of gas so as to contact the top.
 16. The humidification system ofclaim 14, wherein the top is removably coupled to the humidificationchamber.
 17. The humidification system of claim 16, wherein the top isremovably coupled to a bottom portion of the humidification chamber. 18.The humidification system of claim 17, wherein the top is dome-shaped.19. The humidification system of claim 17, wherein the humidificationchamber is at least partially immersed in the liquid of the liquidreservoir.
 20. The humidification system of claim 17, the humidificationcanister further comprising an insulating chamber enclosing thehumidification chamber, the insulating chamber positioned between aninner wall of the humidification canister and an outer wall of thehumidification chamber, wherein the insulating chamber is filled by alayer of insulating gas.
 21. The humidification system of claim 20, thebase unit further comprising a flow divider configured to separate aflow of gas into a first flow directed into the humidification chamberthrough the gas inflow conduit and a second flow directed into theinsulating chamber.
 22. The humidification system of claim 1, furthercomprising a delivery tube in fluid communication with the gas outflowconduit and configured to releasably couple to the nasal cannula totransmit the heated and humidified breathing gas to at least one nare ofa patient.
 23. The humidification system of claim 22, further comprisinga heating source configured to convey heat to breathing gas flowingwithin the delivery tube.
 24. The humidification system of claim 23,wherein the heating source is positioned to heat the breathing gasflowing within the delivery tube.
 25. The humidification system of claim24, wherein the heating source is one of a heated gas and a heatedliquid configured to flow within an outer insulating lumen surroundingan inner lumen through which the breathing gas flows.
 26. Thehumidification system of claim 1, wherein the fluid heater has a heatingplate configured to mate with the heat conducting base of thehumidification canister.
 27. The humidification system of claim 26,wherein the receptacle comprises a circular depression in a bottomsurface of the receptacle, the circular depression sized to fit the heatconducting base of the humidification canister.
 28. The humidificationsystem of claim 1, further comprising: a controller electronicallycoupled to the base unit; and an electronic interface electronicallycoupled to the base unit; wherein the controller is configured tocontrol operation of the blower and the fluid heater based on a userinput at the electronic interface of a set flow rate of the blower and ahumidification setting.
 29. The humidification system of claim 28,further comprising: a temperature sensor operatively coupled to thecontroller and configured to measure one or more breathing gastemperatures; and a water level sensor configured to monitor a level ofthe liquid in the liquid reservoir.
 30. The humidification system ofclaim 1, wherein the gas inflow conduit is configured to be incommunication with first and second gas flow sources, the first gas flowsource providing a flow of air and the second gas flow source providinga flow of oxygen, and wherein the breathing gas flow is a mixture of theflow of air and the flow of oxygen.